It has long been recognized that catheters lose their sterility either in the process of insertion or thereafter. There have been many proposed solutions for the problem, an example of which is U.S. Pat. No. 3,894,540 to F. J. Bonner, Jr. dated July 15, 1975. That patent, and others, disclose the use of a collapsible protective sleeve surrounding the catheter, and while such devices have not been unsuccessful, they do require extremely skillful handling and are not particularly designed for adjustment after the initial insertion into the body of the patient. Such adjustments are particularly necessary when catheters are inserted into the heart for purposes of measuring its activity. It often happens that when the catheter is originally implanted, its tip lodges in an area of the heart which is not sufficiently sensitive. Consequently such cardiac catheters need to be moved about until the end within the heart lodges in a sufficiently responsive area. Such manipulations often require that the end be moved farther into the body, thus requiring that an additional length of catheter be utilized.